1. Field of the Invention
The present invention relates to an improvement of a sewing machine to sew an elastic tape to a fabric.
2. Description of the Prior Art
A generally known elastic tape sewing machine is adapted to place a sewing portion of an elongated elastic tape to be sewn on a fabric, to retain the combined body of the elastic tape and the fabric between feed teeth and a presser foot opposed to the feed teeth, to feed the combined body by the feed teeth and to sew the elastic tape by a sewing needle to the fabric. In this case, the elastic tape is supplied from a tape winding bobbin through a through hole in the presser foot to space between the feed teeth and the presser foot.
Conventionally, in such a sewing machine, the elastic tape to be sewn is fed to have suitable tension on the fabric. Thus, in the course of the elastic tape from the bobbin to the presser foot, the elastic tape is passed between a pair of retaining members pressing the elastic tape. The retaining members are adapted to press the elastic tape by urging a movable retaining member onto a fixed retaining member by the force of a spring.
However, such retaining members can not adjust the force of the spring automatically and precisely. To apply suitable tension to the elastic tape, an adjusting screw may be manually turned on the fixed retaining member to compress the spring inserted between the movable retaining member and the adjusting screw so as to adjust the spring force. That is troublesome and time consuming problem.